Targeting complement anaphylatoxin C5a receptor in hyperoxic lung injury in mice

Complement in trauma-Traumatised complement?

Physical trauma represents a major global burden. The trauma-induced response, including activation of the innate immune system, strives for regeneration but can also lead to post-traumatic complications. The complement cascade is rapidly activated by damaged tissue, hypoxia, exogenous proteases and others. Activated complement can sense, mark and clear both damaged tissue and pathogens. However, excessive and insufficient activation of complement can result in a dysfunctional immune and organ response. Similar to acute coagulopathy, complementopathy can develop with enhanced anaphylatoxin generation and an impairment of complement effector functions. Various remote organ effects are induced or modulated by complement activation. Frequently, established trauma treatments are double-edged. On one hand, they help stabilising haemodynamics and oxygen supply as well as injured organs and on the other hand, they also drive complement activation. Immunomodulatory approaches aim to reset trauma-induced disbalance of complement activation and thus may change surgical trauma management procedures to improve outcome. LINKED ARTICLES: This article is part of a themed issue on Canonical and non-canonical functions of the complement system in health and disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.14/issuetoc.

CDK5RAP1 targeting NF-κB signaling pathway in human malignant melanoma A375 cell apoptosis

Malignant melanoma is characterized by rapid deterioration, early metastasis and high mortality. Cdk5 regulatory subunit-associated protein 1 (CDK5RAP1), which catalyzes 2-methylthio (ms²) modification of mitochondrial transfer RNAs, has been reported to induce cancer cell apoptosis, by a phospho-c-Jun N-terminal kinase (p-JNK) signaling pathway. The present study was the first to report on the association between CDK5RAP1 deficiency and nuclear factor-κB (NF-κB) signaling pathway during the apoptosis process in human malignant melanoma (A375) cells. CDK5RAP1 small interfering RNA (siRNA) and control siRNA were transfected into A375 cells. CDK5RAP1 deficiency inhibited Ca²⁺ influx in A375 cells. CDK5RAP1 deficiency also suppressed the proliferation of A375 cells, induced A375 cells apoptosis, and increased the generation of reactive oxygen species (ROS). In addition, CDK5RAP1 deficiency induced the phosphorylation of NF-κB and Bcl-2/Bcl-xl-associated death promoter (Bad). Notably, the phosphorylation of B-cell lymphoma-xl (Bcl-xl) and B-cell lymphoma-2 (Bcl-2) was downregulated by CDK5RAP1 deficiency. Pretreatment with pyrrolidine dithiocarbamate (PDTC), the inhibitor of NF-κB, prevented the decrease in cell proliferation and apoptosis induced by CDK5RAP1 deficiency in A375 cells. However, pretreatment with PDTC did not affect the generation of ROS in A375 cells, indicating that ROS is an upstream target of NF-κB signaling pathway during the apoptosis process. Taken together, CDK5RAP1 deficiency induces cell apoptosis in malignant melanoma A375 cells via the NF-κB signaling pathway. The results from the present study indicated a potential novel candidate for the treatment of skin cancer.

Protective effects of fucoidan against hyperoxic lung injury via the ERK signaling pathway

High oxygen mechanical ventilation is widely used to treat various lung diseases; however, it may result in hyperoxia, which induces inflammation and lung injury. Fucoidan is an extract of the seaweed Fucus vesiculosus, which has previously been reported to exert effects against diabetic nephropathy. The present study is the first, to the best of our knowledge, to investigate the protective effects of fucoidan against hyperoxic lung injury. Balb/c mice were ventilated with 100% oxygen, with or without the atomization inhalation of fucoidan, for 36 h. Hyperoxia reduced the body weight and increased the relative lung weight of the mice. In addition, cell quantity and differentiation were determined using a hemocytometer, hyperoxia increased the total number of cells, and the number of macrophages, neutrophils and lymphocytes in the bronchoalveolar lavage fluid. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) demonstrated that hyperoxia also increased the mRNA expression levels of cluster of differentiation (CD)68, F4/80, CD64 and CD19 in lung tissue, and induced lung morphological alterations. Furthermore, western blotting assay demonstrated that hyperoxia increased the expression levels of interleukin (IL)‑1, IL‑6 and tumor necrosis factor (TNF)‑α, and the phosphorylation of extracellular signal‑regulated kinase (ERK)1/2. Conversely, hyperoxia‑induced inflammation and morphological alterations were significantly attenuated in the mice treated with fucoidan. Atomization inhalation of fucoidan also reduced the hyperoxia‑induced expression of IL‑1, IL‑6 and TNF‑α, and the phosphorylation of ERK1/2. These findings suggested that fucoidan may attenuate hyperoxic lung injury via the ERK1/2 signaling pathway.

Protective effect of C4a against hyperoxic lung injury via a macrophage-dependent but not a neutrophil/lymphocyte-dependent signaling pathway

Complement anaphylatoxins have been investigated extensively; however, the role of complement anaphylatoxin C4a in hyperoxic lung injury has yet to be investigated. To the best of our knowledge, the present study is the first to demonstrate the role of C4a in hyperoxic lung injury in vitro and in vivo. BALB/c mice were ventilated with 100% oxygen with or without C4a treatment for 36 h. The body weight and the relative lung weight of the mice were determined, along with any morphological changes in the lung. The expression levels of interleukin (IL)-1, IL-6 and tumor necrosis factor-α (TNF-α) were quantified in the lung tissue and bronchoalveolar lavage fluid (BALF) samples by enzyme-linked immunosorbent assay (ELISA) and western blot analysis. The total cell count and the number of macrophages, neutrophils and lymphocytes in the BALF were determined using cytocentrifuge slides and a hemocytometer. Histamine release from total cells in the BALF was also analyzed. The relative mRNA expression levels of CD68, F4/80, CD64, CD19 and CD3 in the murine lung tissue were assessed by reverse transcription-quantitative polymerase chain reaction. The results revealed that hyperoxia induced lung injury and morphological changes, and increased the expression levels of IL-1, IL-6 and TNF-α, histamine release, the number of inflammatory cells, and the expression levels of CD68, F4/80, CD64, CD19 and CD3. The hyperoxia-induced morphological changes and inflammatory reaction were significantly attenuated in mice treated with C4a. Treatment with C4a also attenuated the increase in the total cell count, decreased the number of macrophages in the BALF, and suppressed the elevated mRNA expression levels of CD68 and F4/80 in the lung tissue samples. Conversely, treatment with C4a did not affect the number of neutrophils or lymphocytes in the BALF or the mRNA expression of CD64, CD19 and CD3 in lung tissue. In conclusion, C4a attenuated hyperoxic lung injury via a macrophage-dependent but not a neutrophil/lymphocyte-dependent pathway.

Affect of Early Life Oxygen Exposure on Proper Lung Development and Response to Respiratory Viral Infections

Children born preterm often exhibit reduced lung function and increased severity of response to respiratory viruses, suggesting that premature birth has compromised proper development of the respiratory epithelium and innate immune defenses. Increasing evidence suggests that premature birth promotes aberrant lung development likely due to the neonatal oxygen transition occurring before pulmonary development has matured. Given that preterm infants are born at a point of time where their immune system is also still developing, early life oxygen exposure may also be disrupting proper development of innate immunity. Here, we review current literature in hopes of stimulating research that enhances understanding of how the oxygen environment at birth influences lung development and host defense. This knowledge may help identify those children at risk for disease and ideally culminate in the development of novel therapies that improve their health.